TONWON Battery Tester 12V Car Battery Load Tester Auto Battery Cranking Voltage and Charging System Diagnostic Analyzer

Because of issues with something draining my battery, I started out with a CTEK battery sensor to try and figure out what it was. As mentioned in my review of the CTEK, their unit didn't work out too well, mostly due to the unit not seeming very accurate.The TONWON, on the other hand, seems much more accurate, has much better Bluetooth range (I can now get the battery status without leaving the house to get close to the car), but includes features such as cranking voltage. Highly recommended.If I had one criticism, it is that the app doesn't have the option to specify that you have an AGM battery common to nearly all cars with start/stop technology, so you have to allow for the fact the app will consistently overestimate the charge level slightly (AGM batteries have a slightly higher voltage at any given charge than older 'wet' lead acid batteries). This wouldn't be difficult for them to add, so I'm hoping we'll get this feature.

It does what it says. One minor issue in the help is that they have used ">" when they meant "<" but it is obvious.Let me put the use in context. We have a 4x4 that is not used that much and has lots of electrics, such as electric tailgate. It also has a stop-start battery. As a new battery is not cheap, I wanted to know if (a) I had a faulty battery (car not that old, and I have had many original car batteries last as long as 10 years), or (b) something was running the battery down (we have had the alarm replaced once) or (c) the way it was being used was just not enough to keep the battery topped up.Device is easy to use; Bluetooth range is good enough that I can connect from some places in the house with the car parked outside. The cranking test is handy; the faulty battery was giving too high a cranking voltage when the engine was warm, but I could only see this once the battery was replaced.It was useful to see if a solar panel trickle charger would be enough to compensate for matching the self discharge and "off" battery drain.It logs the run time. I found this useful as I now also have an intelligent battery charger, which has a maintenance mode. With this monitor, I can see that the charger cut in for 2 minutes 33 times in a 24 hour period, which means that the battery discharged by 1Ahr (very approx) in a 24 hour period.There is one shortcoming in this device. There is no setting in the app for battery type. In doing all my research, I discovered that AGM (stop start batteries) have a voltage of 12.8v at 100% capacity (it is 12.6v for normal batteries) and at 12.6v are only around 75% capacity. Thus it really needs a setting for AGM batteries. meanwhile, I have to take the approach that when the voltage gets down to 12.6v, the battery is not 100% but around 75%. Since AGM batteries need to be kept at above 50% if you don't want to shorten their life, I have set the two monitor trip points to 90% and 70% as being closer to 70% and 50% for an AGM battery.As an engineer who has worked on car systems in the past, I know how hard it is to determine a car battery capacity. A bit more information about this device would have been handy - for example, does it learn about the discharge of the battery from a full charge? If so, then there needs to be a "reset" function for when you change the battery.Having said all that, it is a great device. Not least, on the app, you have a battery voltage graph history for days or months, which is something you can show to a garage, so that if you have a problem, you have some evidence e.g. you can see a substantial dip when you unlock the car with the remote locking. I would see this as an essential item for a caravan or boat battery - being able to see the state of charge without having to access them would be really handy.

This seems to work well - fitted in minutes and paired with my Android phone (via the app) instantly. App provides user with real time charge of the battery, cranking voltage and the performance of the alternator via a test. Very handy to keep an eye on the performance of the battery and the alternator.The leads on the device are not that long. If your car has a large battery (my car's battery is a 075) and/or if there is a tight space between the battery and other trim - you may have a problem sitting it somewhere. there isn't much to the device, I paid £39.99 and with hindsight, feels a little expensive.

Great piece of kit, I have an electric car and one of the major issues an electric car can have is the 12v battery failing, this in turn causes a whole world of problems to the electronics of the vehicle, this little gadget puts all that to the curb. Once connected it connects to your phone via bluetooth (within 10m) this then gives an accurate reading of the car whilst it is switched off or on. You can get cheaper 12v plugin adaptors for the cabin which can monitor the level of the 12v battery. However, I don't think these are particulary accurate as you only get a reading when the car is running which will be naturally higher, given the power given to the 12v by the main traction battery. So I opted for this one which I feel is much more accurate. Money well spent in my opinion

Easy enough to fit and connects from quite a bit away. Inside the house through double glazing and car 10yards away using iPhone 12. Keeps detailed history on device that it just uploads to the app whenever it gets connection. Also keeps record of your journeys and checks cranking voltage.I suppose it could have some extra logic for calculating % charge for AGM batteries or temperature compensation using weather service and a temperature chart but it shows the voltage so you can do own calculations and for the money it’s great.

2 weeks on the car and so far has been spot-on. Very useful for tracking down voltage/parasitic drains. Was able to diagnose a faulty/failing battery which a dedicated battery tester and a smart charger both failed to recognise! This device enabled me to see that the battery was losing 0.1v (10%) per 24hrs even when the car was not in use. The data-logging function is the best feature about this device as you can clearly see historical battery state. Fitted a new battery which drops just 0.03v per 24hrs as seen by this device. Further comparisons using this device revealed a slight drain from a dashcam and a cigarette socket adaptor; both of which are not supposed to use anything according to the respective manufacturers! My only complaint is that the bluetooth range is short but then the device is only consuming 1mA power so that it does not become a parasitic load itself.